1. Field of the Invention
The present invention relates to an apparatus and a method for image interpolation, and more particularly, to an apparatus and a method for allocating a new pixel value to a to-be-interpolated pixel of an image frame to improve the resolution of an image corresponding to the image frame.
2. Related Art
Flat panel displays such as a liquid crystal display (LCD) and a plasma display panel (PDP) have rapidly replaced conventional cathode-ray tubes (CRT) in the recent large-sized display market.
While these flat panel displays have a display area and resolution wider and higher than those of CRTs, the flat panel displays deteriorate the picture quality of standard definition (SD) broadcasting images or digital video disc (DVD) images other than high definition (HD) images when the SD broadcasting images or DVD images are displayed on the flat panel displays because these images have a resolution of 720×480i. Furthermore, if the resolution of an image displayed on a flat panel display does not correspond to the resolution of the flat panel display, pixels of the flat panel display are not one-to-one matched to the image, and thus the image is indistinctly displayed on a screen of the flat panel display to cause objective and subject picture quality deterioration. Accordingly, it is necessary to increase the resolution of the image to the resolution of the flat panel display.
Among conventional methods for improving the resolution of an image, the nearest neighbor interpolation that is a spatial interpolation method allocates a pixel value of a pixel of an original image, which is nearest to a target pixel to which a pixel value will be allocated, to the target pixel. This method does not calculate new pixel values and uses the existing pixel values and thus error may be generated and an undesirable phenomenon such as a staircase phenomenon may occur in a magnified image although it has the advantage of high processing speed,.
Furthermore, the bilinear interpolation sums up values obtained by multiplying pixel values of four pixels of an original image, which are nearest to a target pixel to which a pixel value will be allocated, by weights and allocates the summed value to the target pixel. Here, the weights are determined through a linear method and is in inverse proportion to distances between the four pixels and the target pixel. The bilinear interpolation generates less error in an image as compared to the nearest neighbor interpolation although it requires many computing operations. However, the bilinear interpolation allocates a pixel value to an empty pixel only according to calculation of a pixel, and thus blocking effect may be generated.